This invention relates to dasher boards such as those used in hockey arenas and the like, and in particular to a dasher board system that is flexible and can absorb shock imparted by collisions with hockey players so as to provide a safer environment for the players.
Dasher boards, which are used to form the boundary around arenas such as hockey rinks, are by necessity designed to be secure and stable in order to withstand great impact by hockey players skating or being pushed into the boards during the course of a game. Concerns have been raised, however, about the potentially harmful effects of the stiffness or lack of flexibility of the boards (the terms "stiff or flexible" as used herein describe how much the boards move when hit by a hockey player). That is, when a player hits the boards, there exists is potential for injury. If the boards are very stiff the risk of injury increases. It is noted that the faster speed and the more aggressive playing style of hockey players are making the stiffness of the boards an important issue due to the potential for injuries.
There exists a wide range in the stiffness of various dasher board systems. In some systems available today, the top of the boards may move only about 1/16" (relatively stiff) or as much as 2" to 3" (relatively flexible) when hit by a player. Some systems utilize boards that are mounted to a concrete block wall, which tend to be stiff. Conversely, a light, demountable, aluminum dasher board frame, with loose anchors and bolts, will resultingly be flexible.
There are six main components to a typical dasher board system, each of which can affect how stiff the boards feel to the players. These components are the dasher board, the ice retainer, the anchoring system, the connecting system, the shielding, and the shield mounting system.
Dasher boards are made in two general methods; a fixed, continuous frame or in demountable sections which are typically eight feet long. Both types typically have vertical posts with horizontal stringers. The frame material is normally wood, fiberglass, steel or aluminum. The frame is covered with polyethylene or a fiberglass sheet. A greater amount of material in the frame typically provides a more rigid and stiffer frame. This also increases the weight, which makes the boards feel harder because the greater mass resists movement. Fiberglass and aluminum are more flexible than steel and may create a more flexible board.
An ice retainer (or ice dam) is sometimes used for demountable boards. If the dasher boards are removed, the ice retainer keeps the ice from creeping away from the playing surface. If there is no ice retainer, the boards are often frozen to the concrete, which will make the boards stiffer. With the ice retainer, the boards are less likely to be frozen down. The addition of the ice retainer can create an extra joint or place for the boards to pivot on, giving it more flexibility. The thickness of the ice retainer may determine how it affects the stiffness of the boards. The ice is normally one to 11/2" thick. If the ice retainer is 1" thick, the ice may be in contact with the base of the boards. This may cause the boards to be frozen to the ice retainer. If the ice retainer is 2" high, the dasher boards will be above the ice and not frozen down.
The anchors that hold the dasher boards to the concrete can affect how stiff the boards are. For the continuous frames, the posts are welded to anchor plates set in the concrete. This style is normally the stiffest. For the demountable style, an anchor bolt holds the frame to the concrete. More anchors, spaced closer together will make the system stiffer. If too few anchors are used, the ice may push the boards out of alignment. If the anchors are loose, too much movement at the base of the boards may break out chunks of ice along of the boards. It is generally accepted that the base of the boards should be held rigid if they are in contact with the ice.
If there is an ice retainer, there can be two sets of anchors. One set holds the ice retainer to the concrete and the other set holds the dasher boards to the ice retainer or to the concrete behind the ice retainer. The set holding the boards could allow movement between the boards and the ice retainer.
Connecting bolts are used to connect the demountable panels together. Normally there are two or three bolts in the vertical end plate that join one panel to the next in a rigid fashion.
Shielding is normally made of tempered glass or acrylic. Tempered glass is 1/2" thick (6.54 lb/sq.ft.) on the sides of the arena & 5/8" thick (8.17 lb/sq.ft.) on the ends and radius sections. Acrylic is 1/2" thick (3.1 lb/sq.ft.) in all locations. The acrylic is more flexible than the glass and at half the weight, it moves easier when hit. Again we note that less mass offers less resistance to movement. The disadvantage of acrylic is that it is more easily marked up and therefore becomes harder to see through. It also requires better securing than glass when mounted or it will bend when hit and be pushed out of its supports. Glass, which is thicker, is required at the ends to prevent breakage by the puck. Unfortunately, this thicker (and heavier) glass is located where the players tend to hit the boards the most.
The advantage of acrylic is its lighter weight which makes for easier handling. The standard thickness of 1/2" is too flexible to be used in the "seamless" or "supportless" systems without some additional support.
In systems with shield supports, the shields are traditionally mounted between vertical supports (on 4' centers). The supports offer some movement to the shielding. The supports themselves are flexible and they move in the mounting hole and the support bracket. Also, the shielding is held in a gasket that offers some movement. The shielding offers some movement relative to the boards. The shield support could be mounted in a flexible bracket that allows the shield support & shielding to move relative to the boards.
In the new "supportless" or "seamless" style dasher boards, the glass shields are held in a slot or U-channel in the top of the boards. The supportless style holds the glass rigid at the top of the boards. At this point the glass and boards move as one.
FIGS. 1-5 illustrate side views of a traditional prior art dasher board and the various forces the boards are subjected to. FIG. 1 illustrates the dasher board at rest, with no external lateral forces present. FIG. 2 illustrates a lateral force that provides a rotational force about an axis near the interface between the dasher board and the floor. If the boards are hit at the top, the frame pivots about the base slightly and the top of the board moves away from the ice. The upper part of the board moves farther than the lower part. Normally the base of the boards does not lift off the concrete very much. Some designs in the prior art have added springs behind the boards that allow the boards to lift off the concrete, such as in U.S. Pat. No. 4,883,267. In these designs, the ice can deleteriously creep under the boards and prevent it from returning to its rest position.
FIG. 3 illustrates the translational forces that may be imparted on a dasher board assembly. In the prior art, ice may creep into the area near the bottom of the boards, causing misalignment and other problems.
The shielding may also have rotational and/or translational forces subjected thereupon with respect to the boards as shown in FIGS. 4 and 5. As explained below, an improved shock absorbing characteristic of the shielding relative to the boards can be achieved by mounting the shield supports (in the supported design) or the U-channel (in the supportless design) in a fixture that can move within the boards. This would allow the shielding to move away from the playing surface even if the boards did not move.